This invention relates to a voltage regulator, and more particularly to a circuit for regulating battery voltage source.
In many applications, equipment with battery operated power regulation is required. A typical application is for airborne television using a battery operated miniature camera. The problem is to provide a circuit that regulates voltage with maximum utilization of available battery power, i.e., with maximum efficiency.
The prior art has not fully utilized available battery power because the difference between the regulated output voltage and the battery voltage had to be maintained at one volt, or more. That is wasteful at the end portion of the discharge cycle because the final one volt of battery voltage above the regulated voltage can not be utilized.
The graph of FIG. 1 is useful in understanding this problem. A voltage regulator maintains a constant voltage output at some predetermined level substantially below the initial (fresh charge) voltage. When the battery voltage has decayed to a level within a difference .DELTA.V that must by maintained between the regulated output voltage and the battery voltage, the battery is no longer useable.
The useful life of a battery could be extended significantly from time A to time B in the graph of FIG. 1 if its regulated output voltage could be maintained with a difference .DELTA.V that is substantially zero. The importance in thus extending the life of a battery can be appreciated by considering that if a battery life of time B is required, and the regulated output voltage can be maintained with a difference .DELTA.V of almost zero from the battery voltage, a smaller battery may be used. The weight saved with a smaller battery is an important consideration in any battery operated equipment and may be critical in aircraft and space vehicles.